At present, crown-type metal caps are formed by a laminar part of circular plan form having an inner face and an outer face, provided peripherally with a closure skirt and a closure gasket having a peripheral lip located on the inner side of the metal cap. The closure skirt is in turn provided with a plurality of radial projections and depressions interspersed while the peripheral lip of the closure gasket comprises one or more protrusions. These crown-type metal caps are used for sealing the mouth of a glass bottle containing a beverage, that may either be pressurized or not.
The crown-type metal cap to be applied to a glass bottle, offers a hermetic sealing, as the circular plan and the peripheral lip of the closure gasket are tight against the top ring of the mouth of the glass bottle when the cap is applied on it. The protrusions and depressions of the closure skirt of the crown-type metal cap are folded and pressed at the same time through a forming tooling against the ring of the mouth of the glass bottle and slightly below it, providing a proper grip.
The actual crown-type metal cap that is used to seal the mouth of a glass bottle is not suitable for sealing a mouth of a metal bottle, because the metal mouth of a bottle has a different configuration from the mouth of a glass bottle as shown in FIGS. 1, 2 and 3. The mouth of a glass bottle 10 shows a ring 11 having an external diameter D1 and an inner diameter D2 and a top rim 12 and inner rim 13 where at least one of these rims is flat, which helps the sealing by the appropriate seating of the peripheral lip of the closure gasket on said rims. In contrast, the mouth of a metal bottle 20 has a metal ring 21 having an outer diameter D3 and an inner diameter D4 and fully curved edge, so that the outer diameter D3 is generally equal to the inner diameter D1 of ring 11 of the glass bottle 10, while the inner diameter D4 is larger than the outer diameter D2 of ring 11 of the glass bottle 10.
In addition to this, the manufacturing process produces the mouth of the glass bottle to have a constant diameter and because of its material it has a strength that doesn't allow any deformation of the mouth during storage, transportation, filling and sealing of the glass bottle, which produces the proper seating and hermetic closure of the crown-type metal cap. The configuration of the mouth of the glass bottle is standardized by the “Glass Packaging Institute”. In contrast, the mouth of the metal bottle tends to deform during its proper manufacturing process, as well as in storage, transportation, filling and sealing of the metal bottle, which means that the diameter of the bottle mouth presents variations or irregularities that can lead to a non-hermetic closure of the traditional crown-type metal cap.
Therefore, the current crown-type metal cap that is used to seal glass bottles is not entirely favorable to seal metal bottles, since the closure gasket of the current crown-type metal cap is not adapted to compensate for variations present in the finish and the diameter of the mouth of the metal bottle, thus it is necessary to provide a crown-type metal cap with a closure gasket having a design which compensates for such imperfections in the mouth of the metal bottle.